The long-term goal of this research is to develop diagnostic and treatment options for infants under 6 months of age who are at risk for coordination disorders. Clinically, infants are often first diagnosed as 'at risk' at 6-12 months of age when they show delay in several skills such as reaching or walking. Early arm movements (i.e., movements before the development of reaching) offer the potential to detect movement impairments within the first 12 weeks of postnatal life. This project involves the systematic, longitudinal study of joint coordination starting when infants are 4 weeks of age and continuing through successful reaching at 24 weeks. This project is a necessary precursor to the study of young infants at risk for coordination disorders and ultimately to treatments specific to enhancing reaching development. The first aim of this project is to determine the pattern of shoulder-elbow-wrist dynamics from early arm movements through successful reaching. In adults, the appropriate combination of muscular and non-muscular moments at a joint are less complex at the shoulder than at distal points. Shoulder and elbow motion in pre-reaching infants suggests that this dynamic pattern may be present in early movements. If so, this could be an important early marker of typical development. The second aim is to determine the pattern of hip-knee-ankle dynamics from early leg movements up to successful feet reaching, and compare this pattern with that of the arms. Recent work suggests that infants are able to control their legs for reaching weeks before they can control their arms for reaching. Patterns of dynamics underlying feet reaching could help identify atypical development weeks earlier than hand reaching. This project will provide the foundation data for a larger study of the effects of early training on the development of reaching in very young infants at risk for developing coordination disorders such as cerebral palsy. [unreadable] [unreadable]